
## Using Rust to extend Robyn


There may be occasions where Batman may be working with a high computation task, or a task that requires a lot of memory. In such cases, he may want to use Rust to implement that task. Robyn introduces a special way to do this. Not only you can use Rust to extend Python code, you can do it while maintaining the hot reloading nature of your codebase. Making it *feel* like an interpreted version in many situations.



<Row>
<Col>
The first thing you need to is to create a Rust file. Let's call it `hello_world.rs`. You can do it using the cli:
</Col>
  <Col sticky>

    <CodeGroup title="Request" tag="GET" label="/hello_world">

    ```python {{ title: 'untyped' }}
    python -m robyn --create-rust-file hello_world
    ```

    ```python {{title: 'typed'}}
    python -m robyn --create-rust-file hello_world
    ```

    </CodeGroup>
  </Col>
</Row>
<Row>

  <Col>
  Then you can open the file and write your Rust code. For example, let's write a function that returns a string.


  </Col>
  <Col sticky>
    <CodeGroup title="Request" tag="GET" label="/hello_world">

      ```rust
      // hello_world.rs

      // rustimport:pyo3

      use pyo3::prelude::*;

      #[pyfunction]
      fn square(n: i32) -> i32 {
          n * n
          // this is another comment
      }

      ```

    </CodeGroup>
  </Col>
</Row>

<Row>

  <Col>
  Every Rust file that you create using the cli will have a special comment at the top of the file. This comment is used by Robyn to know which dependencies to import. In this case, we are importing the `pyo3` crate. You can import as many crates as you want. You can also import crates from crates.io. For example, if you want to use the `rusqlite` crate, you can do it like this:



  </Col>
  <Col sticky>
    <CodeGroup title="Request" tag="GET" label="/hello_world">

      ```rust
      // rustimport:pyo3

    //:
    //: [dependencies]
    //: rusqlite = "0.19.0"

      use pyo3::prelude::*;

      #[pyfunction]
      fn square(n: i32) -> i32 {
          n * n * n
          // this is another comment
      }

      ```

    </CodeGroup>
  </Col>
</Row>


<Row>
  Then you can import the function in your Python code and use it.

  <Col sticky>
    <CodeGroup title="Request" tag="GET" label="/hello_world">

      ```python {{ title: 'untyped' }}
      from hello_world import square

      print(square(5))
      ```

      ```python {{title: 'typed'}}
      from hello_world import square

      print(square(5))
      ```
    </CodeGroup>
  </Col>

  To run the code, you need to use the `--compile-rust-path` flag. This will compile the Rust code and run it. You can also use the `--dev` flag to watch for changes in the Rust code and recompile it on the fly.

  <Col sticky>
    <CodeGroup title="Request" tag="GET" label="/hello_world">

      ```python {{ title: 'untyped' }}
      python -m robyn --compile-rust-path "." --dev
      ```

      ```python {{title: 'typed'}}
      python -m robyn --compile-rust-path "." --dev
      ```
    </CodeGroup>

  </Col>
</Row>

An example of a Robyn app with a Rust file that using the `rusqlite` crate to connect to a database and return the number of rows in a table: https://github.com/sansyrox/rusty-sql


## What's next?


Batman was curious to know what else he could do with Robyn. 

Robyn told him to keep an eye on the GraphQl support.

[GraphQl Support](/documentation/en/api_reference/graphql_support)







